Internal firing switch means for electrically fuzed projectiles



March 1968 J. BROTHERS 3,372,642

INTERNAL FIRING SWITCH MEANS FOR ELECTRICALLY FUZED PROJECTILES Filed Aug. 6, 1964 JACK BROTHERS M 1. hug,

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United States Patent 3,372,642 INTERNAL FERENG SWITCH MEANS FOR ELECTRICALLY FUZED PRQJECTILES Jack Brothers, Succasunna, N.J., assignor to the United States of America as represented by the Secretary of the Army Fiied Aug. 6, 1964, Ser. No. 388,352 2 Claims. (Cl. 102-70.2)

ABSTRACT OF THE DHSCLOfiURE The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

The present invention relates to electrically fuzed projectiles of the hollow, cylindrical, explosive-carrying shell type that crush and explode after impact in response to operation of internal firing switch means.

In certain military applications, it is desired that this type of projectile crush back to a certain point along its length and then function or explode. The fuze-firing switch is generally located at this point for operation by crushing action on the projectile. The switch is connected serially in circuit with the fuze and a suitable electric current source so that when the switch operates or closes, the fuze is activated by the electric current to ignite the explosive charge and detonation follows.

Present firing or crush-switch mounting in projectiles of this type generally involve the use of a probe element extending centrally from the fuze into the body or charge of explosive material or explosive filler in the casing with which the projectile is generally provided. The switch means is carried at the forward end of the probe element in the area of the crush point.

It has been found that this construction is subject to certain operating difiiculties. The switch may be subject to premature closing by the columnar action or longitudinal displacement of the explosive filler or charge when the projectile is crushing on a hard target such as armor. The crush switch held by a probe displaces explosive material and thus reduces the amount of charge that can be used in a given projectile.

These problems have been solved not too satisfactorily, in the past by decreasing the operating sensitivity of the firing or crush switch and by increasing the thickness of the metal to be crushed, such as the shell walls, for example. However, decreasing the operating sensitivity of the switch or increasing the resistance of the projectile to the crush action by which the switch is operated, renders the projectile less reliable at oblique impacts. Thus these and other expedients are not fully satisfactory.

It is, therefore, an object of this invention to provide improved firing-switch means for electrically-fuzed projectiles of the type referred to which is simple in construction and reliable in operation at all angles of impact, with a high degree of sensitivity.

It is a further object of this invention to provide, in an electrically-fuzed projectile of the shell type, improved internal firing switch means that prevents closing by columnar or like action of the explosive filler or charge in the projectile when crushing on a hard target, and which reduces the amount of the explosive filler or charge which is displaced thereby to a minimum.

Patented Mar. 12, 1968 ice In accordance with one embodiment of the invention, in a projectile having a hollow metallic casing or shell for an explosive filler or charge, there is provided a circumferential firing switch in said casing as a deformable or crushable relatively-thin liner along the inner wall thereof.

The switch comprises a tubular sheet-metal, or otherwise conductive, liner element for said inner wall extending rearwardly from a desired crush point, at which the fuze is to be activated and providing one pole of the switch. This element is relatively thin-walled and readily deformable or crushable. It is separated from the other pole of the switch, which is the inner wall of the conductive metal shell or projectile body, by a relatively thin crushable sleeve or liner of insulating material interposed between it and said wall, in close contacting relation.

The switch is thus subject to closure by deformation or crushing with the casing wall, beginning at the crush point, and direct contact between the conductive liner element and the casing wall through the crushed and ruptured insulating sleeve or liner. The electrical fuze for the projectile is connected in circuit with the suitable current source between the casing and the conductive liner element thus to be activated by the switch closure.

The invention will further be understood from the following description when considered with reference to the accompanying drawing, and its scope is pointed out in the appended claims.

In the drawings:

FIG. 1 is a section view, in elevation, of a projectile of the shell type provided with an electrical fuze and internal firing switch means therefor in accordance with the invention,

FIG. 2 is a section view of the projectile of FIG. 1 taken on the section line 22,

FIG. 3 is a schematic circuit diagram showing the prior art relation of fuze and switch means in a projectile of this type, and

FIG. 4 is a schematic circuit diagram of the projectile of FIGS. 1 and 2 showing the operation therefor on impact in accordance with the invention.

Referring to the drawing wherein like elements in the several figures are designated by like reference numerals, and referring particularly to FIGS. 1 and 2, 6 is a cylindrical, hollow, explosive-carrying projectile casing or shell having a forward thin-walled nose 7 and a thicker-walled base end 8. The latter is fitted with a threaded plug 9 which closes the hollow interior chamber 10 to retain the explosive filler or charge 11 therein. The shell and plug may be of steel and the shell is of a size to fit the riding in the bore of a gun (not shown) by which it may be fired. The usual gas sealing rings 12 of copper or the like are indicated. This projectile is shown by way of example as representing any electrically-fuzed projectile of the shell type that crush following impact, and explode in response to operation of internal firing switch means.

Referring to FIG. 3 along with FIGS. 1 and 2, the electrical fuze structure or casing is indicated at 15 and is located in contact with the body of explosive material and preferable in connection with the rear plug 9 by which it may be removed. In the prior art structure or conventional mount, the fuze structure or casing is provided with an operating switch 16 mounted on the outer forward end of an elongated central support element or probe 17 extending longitudinally forward from the fuze, all as indicated in dotted outline in FIGS. 1 and 3, since it does not form part of the present switch structure.

The switch 16 of the prior art structure may be of the two-pole normally-open type as indicated, and connected through two insulated conductors 19 and 20, respectively, with the fuze cartridge 18 and a source of firing current such as a battery 22 in the casing 15. A conductor 23 connected from the battery 22 to the fuze cartridge 18 completes the series firing circuit for the switch 16.

The switch is of the crush type, that is, it closes or operates when deformed or crushed as the shell crushes at a point along its length as indicated by the letter C and arrowed lines in FIG. 1 and performs the desired function. However, it will be seen that the crush switch construction on the forward end of a probe is subject to the operating difficulties referred to. These include the premature closing by the columnar action or slight longitudinal displacement of the explosive filler or charge 11 without the desired penetration of the target and crush of the shell on a hard target. Also the probe and switch construction necessarily displaces a considerable quantity of explosive that otherwise could be provided.

The switch construction of the present invention replaces the probe and switch construction as above described and eliminates the difficulties referred to. Referring again to FIGS. 1 and 2, along with FIG. 4, the hollow-metallic casing or shell 6 is provided with a relatively-thin circumferential or tubular firing switch 25 as a deformable or crushable liner therefor along the inner wall thereof. Thus it occupies effectively no space that detracts appreciably from the charge-carrying capacity.

The switch comprises a tubular, thin-walled, electrically-conductive liner element 26 for the inner Wall extending rearwardly from the crush point or area C and providing one pole of the switch. It is separated, throughout its length, from the other pole of the switch, which is the casing or inner wall thereof, by a relatively-thin crushable sleeve or second liner element 27 of electrical insulating material interposed between it and said wall in close contacting relation. The two sleeve or liner elements are thus in close-fitting nested relation against the inner wall of the casing.

As indicated in FIG. 4, the inner conductive liner or switch element 26 is connected with the fuze or fuze cartridge 18 and the source 22 of firing current in a firing circuit that is completed from the switch element 26 through a conductor 28 to the source or battery 22 and thence through the lead or conductor 23 to the fuze 18. These elements may be included in the casing 15 for the compactness and easier mounting. Since the opposite pole of the switch is the casing 6 or the inner wall thereof, the firing circuit is connected therewith by a return conductor 29, from the fuze to the cap 9 by which it is carried, and thence to the other switch element which is the casing or casing inner wall.

As indicated at 30 in FIG. 4, when the casing crushes, the two liner elements 26 and 27 do likewise. Direct contact between the conductive liner element 26 and the casing wall results in effective switch closure through the ruptured insulating liner element 27 as indicated. Thus firing current flows from the source 22 through the fuze cartridge 18 and detonation of the charge results.

This improved switch construction for electrically-fuzed projectiles prevents premature closing and loss of charge space as hereinbefore described with respect to conventional devices of this type. The metal wall thickness of the shell does not have to be changed to decrease the sensitivity of the crush switch. Hence a high degree of sensitivity can be maintained for random and oblique hits, as is desirable, with this improved shell and switch construction.

The switch 25 can be assembled to the inner shell wall as a thin-walled tubular unit, as above described, or the two liner elements 26 and 27 can be assembled in the casing by cementing to the inner wall of the shell. In any case, a simplified and relatively low cost construction is attained while maintaining reliability in operation.

I claim:

1. In a projectile, the combination with an electricallyconductive cylindrical shall casing for an explosive charge, of an electrical fuze in the casing for firing said charge, and a tubular firing switch in said casing as a relativelythin liner therefor along and closely fitting the inner wall thereof, said switch including a relatively thin-walled tubular electrically-conductive liner element for said inner wall, means connecting said liner element and casing in circuit with said fuze for supplying operating current thereto upon contact with said casing wall to activate the fuze and fire the charge, and a thin-walled rupturable sleeve of insulating material extending along the length of said liner element and tightly-fitted between said liner element and the casing wall in close contacting relation therewith for maintaining said liner element out of contact with said wall and the switch in an open condition prior to impact and rupturing of said sleeve to close said switch.

2. In an electrically-fuzed projectile of the hollow shell type for carrying and firing an explosive charge, the combination with an elongated cylindrical hollow casing therefor, of an electrical fuze mounted in one end of said casing, a source of firing current for said fuze, a firing switch for said fuze assembled to the casing inner wall as a thin-walled tubular unit in close engagement therewith, said switch comprising two nested cylindrical liner elements, one being of relatively-thin and rupturable insulating material and the other being of relativelythin electrically-conducting material said insulating liner being in tightly contacting relationship throughout the length of said conductive liner, the insulating liner element being in contact with the casing wall which provides one switch pole and maintaining said wall from contact with the conductive liner element as the second switch pole, and means providing a firing circuit for the fuze connected from the casing and the first switch pole through the fuze and current source to the second switch pole and completed by the effective switch closure upon impact and rupturing of the insulating liner ele ment. 9

References Cited UNITED STATES PATENTS 914,371 3/1909 Davis 102-70.2 X 2,887,056 5/1959 Perret 10270.2 3,111,089 11/1963 Dodson 10*2-70.2 3,188,960 6/ 1965 Samburoff l0270.2

BENJAMIN A. BORCHELT, Primary Examiner.

W. C. ROCH, V. R. PENDEGRASS,

Assistant Examiners. 

